1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor package, and in particular, relates to a method for manufacturing a semiconductor package while using a die having an ejector pin, the semiconductor package having a mirror-finished surface encircled by a satin-finished surface.
2. Description of the Related Art
A typical semiconductor package is formed by embedding an IC structural. body having a lead, an IC chip, and bonding wires bonding between the lead and the IC chip within a resin bulk while using a die.
A surface of the die, as its normal appearance, is generally a satin-finished surface for the sake of easy exfoliation.
In such a prior art that is disclosed by “Nakagawa et al., Kata-Gijyutu-Binran, Nikkan-Kogyo-Shimbun, 1989, p. 88-95”, a circular and concave imprint formed by an ejector pin, which is a mirror-finished surface, is used as an indicator of a “1-pin” for recognition of a first pin. The ejector pin is arranged in the die during a process of resin-encapsulation to readily release the semiconductor package from a die after the resin-encapsulation. When the ejector pin moves, an imprint of the ejector pin is formed on the satin-finished surface of the semiconductor package.
When plural imprints are formed, the “1-pin” is formed while having specific shape and appearance which are distinguishable from imprints of the other pins.
Japanese Patent Kokai 11-87565 (document D1) discloses another method for forming an indication portion of the “1-pin” on a package surface. In this method, a portion corresponding to the indication portion is made at a step of forming a satin-finished surface on the die by finishing the surface excluding a masked portion with plasma-etching etc.
After encapsulation of the IC structural body with a resin, a mark representing a product name, etc. is stamped on a surface of the semiconductor package released from the die as disclosed by a Japanese Patent Kokai 2001-160604 (document D2). As for the method for stamping a mark on the package surface, the mark is formed by a laser beam in view of its fast processing speed.
Recently, in a resin-encapsulation-type semiconductor package, in particular, a semiconductor package for an IC card, a thin thickness and a compactness are required, so that a resin layer covering the semiconductor package is made thinner.
It is, on the other hand to, be understood that the above-mentioned imprint of ejector pin influences an installment height of the semiconductor product, the imprint can not be formed as convex and is normally formed as concave.
For this reason, as a thickness of manufactured semiconductor package decreases, it is difficult to keep a space between the concave portion of the imprint of ejector pin and the bonding wires in the semiconductor package. There arises a problem that the bonding wires are subject to be exposed to the outside during the resin-encapsulation.
The laser stamping is typically performed by etching a resin surface of tens micrometers. When a thickness of the resin surface of semiconductor package is much thin, a depth of the mark to be formed by the laser beam can not be disregarded. There arises another problem that an IC structural body such as bonding wires etc. is exposed to the outside by way of etching the resin surface during resin-encapsulation and that a resin wall cracks at the laser stamped portion because of an external pressure.
In addition, a mirror-finished surface of a die is likely to be deteriorated much more than a satin-finished surface of the die, so that the mirror-finished surface is deteriorated earlier when the die is used repeatedly. In the die disclosed by document D1, a mirror-finished surface used for indicating directly the “1-pin” position is formed on an upper inner wall surface of the cavity which is a satin-finished surface. When the mirror-finished surface is deteriorated, it is required to replace one or all parts of die for new one even though the portion of satin-finished surface is not deteriorated. As a result, there arises another problem that mass-production of semiconductor package causes to raise costs for the die.